Near Field Communication (NFC) is a standards-based short-range wireless connectivity technology for electronic devices to establish communication with each other by bringing them into close together (typically 0-5 centimeters). NFC is possible between NFC devices and also between an NFC device and an unpowered NFC device, which is called a tag and similar to a Radio-Frequency Identification (RFID) tag.
NFC antennas behave as inductors to operate at low frequency (long wavelengths) on electronic devices based on mutual coupling. In general, larger inductance of the NFC antenna brings better performance thereof. Typically, a loop of wire around a material gives a strong magnetic field within the loop. Hence, NFC antennas are often simply loops of wire or a coil, occupying as much surface area as the electronic device allows.
Therefore, how to increase the magnetic field induced by the NFC antenna has become a topic in the industry.